Apparatus for generating a digital video picture

ABSTRACT

An apparatus for generating a digital video picture is proposed. In this case, the video picture comprises a main picture and a secondary picture. The secondary picture serves to provide information about the status of the apparatus or else for operational guidance. The data of the picture are supplied digitally. Data for the subpicture are additionally contained in the bit stream for the main picture. The subpicture can likewise be displayed together with the main picture and provide information such as, for example, subtitles with respect to the main picture. Decoding apparatuses for the main-picture data and the subpicture data are provided. Also provided is a multiplexing device for the correctly timed outputting of the decoded data and, consequently, of the joint representation of main picture and subpicture. The apparatus has a storage device, in which data for the secondary pictures are stored in coded form. The coded data of a secondary picture are loaded into the decoding unit for the subpicture data in response to a received command. The decoding of the data for the subpicture is stopped and the decoding of the data for the secondary picture takes place instead. In a further refinement of the invention, provision is additionally made of a second subpicture decoding device, which is used for the decoding of the displayable secondary pictures. In this case, subpicture and secondary picture can then be inserted simultaneously in the video picture.

The invention relates to an apparatus for generating a digital videopicture, the video picture being composed of a plurality of components,in particular main picture and secondary picture.

BACKGROUND OF THE INVENTION

The invention is based on an apparatus for generating a digital videopicture of the generic type of the independent claims 1 and 2. In videotechnology, it is known to provide so-called subpicture decodingdevices, for example in a DVD playback device, for displaying forexample subtitles on the screen of a television set. DVD playbackdevices of this type are already commercially available and contain theabovementioned subpicture decoding device. However, such subpicturedecoding devices also come into consideration in the context ofreceivers for digital television (set-top box). The abovementionedsubpicture decoding units are already commercially available andcorrespondingly known to the relevant person skilled in the art. Adescription of the subpicture decoding devices is found, moreover, inthe DVD standard DVD Specifications for Read-Only Disc, Part 3, VideoSpecification, Version 1.0, Aug. 96, 5.4.3 Sub Picture Unit (SPU). Adetailed description of such subpicture decoding devices is also foundin EP-A-0 725 541.

In the case of the abovementioned electronic equipment (DVD playbackdevice and set-top box), it is customary, as in the case of otherequipment appertaining to consumer electronics, too, to insert statusinformation from the respective equipment in the output video picture.In addition, the use of so-called on-screen display menus (OSD) foroperational guidance is widespread. Such menus relate for example to thesetting of the volume in the case of a television set with the aid of adisplayed bar indicator, the setting of balance, colour contrast,brightness, etc. in the case of a television set, the selection of aprogramme location by means of a displayed table with regard to thestored TV programme locations in the case of a television receiver,specific menus for the programming of a video recorder and so on. Inorder to generate such OSD menus or else status displays, use isnowadays usually made of specialized microcontroller circuits withinternal or external ROM and RAM memories. These circuits are usuallydesigned in such a way that the dot matrix-like pattern for eachdisplayable character is stored in the ROM memory. Graphics characterswith the aid of which, for example, the corresponding bar charts can becomposed may also be mentioned as displayable characters. For an OSDmenu, the requisite character codes are then transferred to a charactergenerator, which removes the associated dot matrix data from the ROM andgenerates the associated RGB signals at the correct locations in thepicture and inserts them in the picture. The solution can also beconfigured for equipment with digital signal processing (includingdigital frame store) in such a way that the pixel data are generatedindividually by the character generator and written to the frame storeat the corresponding locations.

If such a conventional OSD circuit is additionally used for theinsertion of status information and menus for operational guidance inthe abovementioned equipment (DVD playback device, set-top box, etc.),then the problem arises that not only the already mentioned subpicturedecoding unit must be implemented with hardware outlay but also the OSDcircuit. This causes increased costs in the development of the equipmentsince it is necessary to develop and adapt two very different circuitsfor the insertion of subpictures/secondary pictures.

SUMMARY OF THE INVENTION

An inventive arrangement reduces costs associated with providingcircuitry for generating operational menus and status information inequipment with an integrated subpicture decoding unit. In a firstinventive arrangement an existing subpicture decoding unit is, inaddition, advantageously used for generating status information oroperating menus. To this end, it is provided that the equipment has astorage device in which the data for the displayable status informationor operating menus are stored in a correspondingly coded form. The datafor such secondary pictures are loaded into the subpicture decodingunit, following a request by means of a corresponding command, and arethen decoded in the decoding unit after the decoding of data for apossibly activated, different subpicture (for example subtitles) hasbeen stopped. In the case of this solution, then, the insertion ofsubtitles is suppressed and, instead, the secondary picture with thestatus information or the operating menus is displayed. However, this isnot necessarily disadvantageous since the user generating the exemplarymenu command will wish to view the operating menu in any case.

In a second solution according to the invention, a second subpicturedecoding unit for the status information and operating menus is providedin addition to the subpicture decoding unit for the outputting of thesubtitles. Both subpicture decoding units may be constructed similarlybecause the data for the operating menus and status information arecoded according to the same coding rules as the data for the subtitles.Although it is necessary to provide a second subpicture decoding unit inthis solution, the implementation outlay is considerably reduced sinceboth subpicture decoding units are constructed similarly. The advantageof this solution consists principally in the fact that subtitles andoperating menus and/or status information can be inserted simultaneouslyin the video picture. This is advantageous particularly when statusinformation such as, for example, time of day, playing time, date,remaining playing time, etc. are to be added to the picture.

In a third solution according to the invention the two separatesubpicture decoding units of the second solution are combined to form acommon decoding unit. However, this presupposes that the subpicturedecoding unit has sufficient memory to store the data of two differentsubpictures and to process the data successively with correct timingthroughout the duration of a video frame or field.

The following holds true for all three solutions: if only simple OSDmenus are intended to be displayed, for example the insertion of simplesymbols for the display of the operating mode, it is not absolutelynecessary to load the data of the subpicture units into the subpicturedecoding units if the subpicture decoding devices are designed in such away that they can decode the associated data directly from thenon-volatile memory (ROM).

The solutions according to the invention have the following advantagesin addition to the advantages already mentioned. The data for asubpicture contain, firstly, the so-called bit map data for thesubpicture and, secondly, the so-called display control commandsequences. By virtue of the fact that bit map data for the subpicturesare used, practically any desired configurations are easily possible forthe OSD menus. It is also advantageous that the bit map data are runlength coded. This saves memory space.

The fact that the subpicture decoding unit decodes the bit map data in aline-oriented manner means that it is not necessary to buffer-store theentire decoded subpicture in a memory. This also saves memory space.

DRAWINGS

Exemplary embodiments of the invention are illustrated in the drawingsand are explained in more detail in the description below.

In the figures:

FIG. 1 shows the display of a subpicture and of a status informationitem on the screen of a television receiver;

FIG. 2 shows examples of different status information items and anoperating menu;

FIG. 3 shows an example of a frame format for the data of a subpicture;

FIG. 4 shows a diagrammatic illustration of the rules for run lengthcoding of the pixel data of a line of a subpicture;

FIG. 5 shows four examples of status information items and associatedrun length coding words;

FIG. 6 shows an example of a subpicture unit which is used to insert astop symbol on the screen;

FIG. 7 shows a block diagram of the first apparatus according to theinvention;

FIG. 8 shows a flow diagram for a program for controlling the subpicturedecoding device in accordance with the first solution according to theinvention;

FIG. 9 shows a block diagram of the second solution according to theinvention; and

FIG. 10 shows a refined block diagram of the subpicture decoding unit inaccordance with the third solution according to the invention.

DESCRIPTION OF THE INVENTION

In FIG. 1, the reference numeral 10 designates a conventional TV set.The reference numeral 14 designates a DVD playback device. The latter isconnected to the TV set 10 via a coaxial lead, for example. The DVDplayback device 14 generates the analog television signal which is fed,for example, to the TV set 10 via the antenna socket. The referencenumeral 13 designates the main picture or background picture. Thereference numeral 11 designates an inserted secondary picture, whichconveys the status information depicting, for example a “playback mode”for the DVD playback device 14. The reference numeral 12 designates aninserted subpicture, which is provided for displaying subtitles. Thisinserted subpicture is illustrated by dashed lines since, in accordancewith the first solution according to the invention, it would not bevisible at the same time as the secondary picture 11.

Examples of inserted secondary pictures are shown in FIG. 2, withsymbols for playback mode, stop mode, pause mode, fast-forward mode,fast-reverse mode, skip forward, skip backward, playing time, time ofday and date as examples of status information items. Furthermore, thelower part of the FIG. 2 illustrates a programme location table as anexample of an operating menu. The currently set programme location isemphasized by a background. This operating menu may be provided forexample for an item of equipment for receiving digital televisionsignals (set-top box).

FIG. 3 gives a rough illustration of the known data format of aso-called subpicture unit (SPU). Such a subpicture unit is respectivelyprovided for a subtitle in the picture. The reference numeral 20designates a data field for a header (SPUH) of the subpicture unit. Thereference numeral 21 designates a data field for the compressed pixeldata of a first field of the subpicture (PXDTF), and the referencenumeral 22 correspondingly designates a data field for the compressedpixel data (PXDBF) of the second field of the subpicture. Finally, thereference numeral 23 designates a data field for a display controlcommand sequence table (SP_DCSQT). So-called display control commandsequences (SP_DCSQ) are stored in the data field 23. The arrangement ofthe PXDTF and PXDBF data is one possible example of such an arrangement.It may also be chosen differently, however. The individual displaycontrol commands will not be discussed in more detail in this patentapplication because they are individually explained with a high degreeof accuracy for example in the known DVD standard (Version 1.0), withthe result that, therefore, reference is expressly made to thispublication for the disclosure of the invention.

The pixel data in the data fields 21 and 22 determine the displayedpattern of the subpicture. For each pixel of a line of the subpicture, adata word two bits wide specifies whether the pixel is a backgroundpixel or a foreground pixel or whether the picture is to be highlightedin a first manner or in a second manner. These four distinctions can bemade using the two bits. Specifically, these binary values denote:00=background pixel, 01=foreground pixel, 10=pixel displayed withhighlighting 1, and 11=pixel displayed with highlighting 2.

It must be taken into account here that the individual pixel data arenot stored in this pure form in the memory, but rather in compressedform. Run length coding is carried out for this purpose. The run lengthcoding method is explained in more detail below with reference to FIG.4.

Seven coding rules are stipulated for run length coding in the DVDstandard mentioned. The run length coding operates such that arespective line of a field of the subpicture to be displayed is runlength coded. The first rule for run length coding reads as follows:

1. If one to three pixels having the same data word follow one anotherin the line, then the number of pixels is entered in the first two bitsof the first run length coding word and the pixel data word is enteredin the succeeding two bits. Four bits are then regarded as a unit. Thisis illustrated in the top part of FIG. 3. The reference numeral 30designates the data field for the number of pixels, which data field hasa memory space for two bits. The reference numeral 31, on the otherhand, designates the data field for the type of pixel, that is to saythe data word of the pixels. This data field likewise has a length oftwo bits.

The second rule for run length coding reads as follows:

2. If four to fifteen pixels having the same data word follow oneanother, then a zero is entered in the first two bits of a run lengthcoding word, and the number of pixels is entered in the next four bits,and the type of pixel is again entered in the last two bits. Thisresults in a run length coding word having a length of eight bitscorresponding to the second part of FIG. 4.

The third rule for run length coding reads as follows:

3. If sixteen to sixty-three pixels having the same value follow oneanother, then a zero is entered in the first four bits of the run lengthcoding word and the number of pixels is entered in the next six bitsthat follow. The type of pixel is again entered in the last two bits.This produces a run length coding word having a length of twelve bits.This is illustrated in the middle part of FIG. 3.

The fourth rule for run length coding reads as follows:

4. If sixty-four to two hundred and fifty-five pixels having the samevalue follow one another, then a zero is entered in the first six bitsof the run length coding word, and the number of pixels is entered inthe following eight bit positions, and the type of pixel is entered inthe next two bits. This produces a run length coding word having a widthof sixteen bits, which is illustrated at the penultimate position inFIG. 3.

The fifth rule for run length coding reads as follows:

5. If the same type of pixel runs right to the end of the line, then azero is entered in the first fourteen bit positions and the type offollowing pixel is entered in the last two bit positions. This againproduces a run length coding word having a width of sixteen bits, whichis regarded as a unit. This word is illustrated in the last part of FIG.4.

The sixth rule for run length coding reads as follows:

6. If, on the basis of the run length coding, no integral byte divisionof the run length coding words is possible for the entire line, then, atthe end of the line, four zeros are entered in the last bit positions.

Further, the following is used as the last rule for run length coding:

7. The quantity of run length coded data within a line shall correspondto one thousand four hundred and forty bits or less.

Given simple picture contents, a large degree of compression is achievedby the run length coding. Examples of run length coding words arespecified in FIG. 5. Four examples of status information items of a DVDplayback device are illustrated in this case. They are, from top tobottom, the status information items of stop mode, playback mode, fastforward mode and skip forward. The associated symbols to be displayedare respectively specified in the left-hand part of FIG. 5. All of thesymbols comprise 9×13 pixels. Asterisks represent respective pixels thatare to be coded as a foreground pixel. Dots represent the backgroundelement. The form in which the run length coding was carried out foreach line of the symbols is in each case specified on the right next tothe respective line. In this case, the abbreviation BP denotesbackground pixel. The abbreviation PP correspondingly denotes foregroundpixel (pattern pixel).

The resulting data bits for the run length code are then in each casespecified in hexadecimal nearest decimal notation at the right-hand edgeof FIG. 5. These data, associated with at least one display controlcommand sequence (SP_DCSQ) in which the associated symbol is placed intothe top right corner of the screen, represent the data of an associatedsubpicture unit.

An example of a program for inserting the stop symbol in accordance withFIG. 5 on the screen is illustrated in FIG. 6. The part designated bySPUH corresponds to the header of the subpicture unit. The size of thesubpicture unit is specified therein by the command SPDSZ. All of thenumbers in the left-hand part of FIG. 6 are hexadecimal numbers. Decimalnumbers are specified in the right-hand part of FIG. 6. The start of theprogramme area for the display control commands is specified by thecommand SP_DCSQTA. The PXD area contains the bit map data for the stopsymbol (see FIG. 5). The first and second fields are listed one afterthe other in this area. The data for lines 1, 3, 5 and 7 correspondingto the first field come first and then the data for lines 2, 4, 6 and 8corresponding to the second field.

The display control commands are successively listed in the areaSP_DCSQT. The command SP_DCSQ_STM defines the instant at which thedisplay control command sequence is to be processed. This examplecontains merely one display control command sequence, which is starteddirectly after the start of the subpicture unit. The commandSP_NXT_DCSQ_SA points to the beginning of the next display controlcommand sequence. In this example, the beginning of the single displaycontrol command sequence is specified here, with the result that thedisplay control command sequence is endlessly repeated. The colour ofthe pixels of the subpicture unit for background and foreground etc. isdefined by the command SET_COLOR. The next command SET_CONTR sets thecontrast for the pixels of the subpicture unit. The command SET_DAREAspecifies the x and y coordinates for the start and end points of thedisplayed rectangular area in the picture. The command SET_DSPXAspecifies the beginning of the area with the bit map data for the firstand second fields. The display of the symbol to be displayed is startedby the command STA_DSP. The end command CMD_END indicates the end of thedisplay control command sequence. As already mentioned, in the exampleillustrated, the display control command sequence is endlessly repeated,until the subpicture unit SPU is stopped by timeout or by externalintervention in a control register of the subpicture decoding unit onthe part of the external CPU. The user can initiate this action, forexample, by pressing a key on the remote control.

A first block diagram of the arrangement according to the invention willnow be explained with reference to FIG. 7. The reference numeral 41designates a serial data input. Here, a bit stream is present whichcontains both video data and audio data as well as the data for thesubtitles to be displayed. The data may either have been read from anoptical storage disk (DVD) or have been received via anantenna/satellite antenna or a broadband cable from a broadcastingstation. The apparatus would be used in a DVD playback device in thefirst case, and in a satellite receiver or a set-top box for digitaltelevision reception in the other cases. The incoming data are thenfirst of all subjected to error detection and correction in a correctionunit 42. The data subsequently pass into a separator circuit 43, inwhich the video, audio and subpicture data, which are still mixedtogether, are separated and are in each case transferred accordinglyeither to a video decoding unit 44, a subpicture decoding unit 45 or anaudio decoding unit 46. The decoded video and subpicture data are inputinto a multiplexing unit 47. The multiplexing unit 47 is controlled bythe subpicture decoding unit 45. At the output of the multiplexing unit47, the data for the individual pixels of the video picture aresuccessively entered into a TV signal coding device 48. At the outputsof the TV signal coding device, the standard-conforming luminance andchrominance signal (Y,C) is output in digital form (PAL, SECAM, NTSC).These signals are subsequently converted into analog signals in thedigital/analog conversion unit 49 and forwarded to corresponding outputs56, 65. The associated audio signal is already generated in astandard-conforming manner in the decoding device 46 and is convertedinto an analog audio signal (only a mono signal is illustrated here) inthe digital/analog conversion unit 50. This audio signal is madeavailable at the output 58.

The design may, on the other hand, also be such that the analogluminance and chrominance signal and the audio signal are modulated ontodifferent carriers in a modulation unit 51 and output as a correspondingTV signal via just one output 57.

In addition, an infrared input is designated by the reference numeral52. This input is used to receive the infrared signals from a remotecontrol unit. The corresponding interface circuit which analyses thereceived infrared signals is designated by the reference numeral 53. Thereference numeral 54 designates a microcontroller. The latter alsoreceives the conditioned command words from the infrared interface 53.The microcontroller 54 also serves to control the units 42-46 via acorresponding control bus. Control is effected for example by theabovementioned units being initialized to specific starting values. Inthe event of an IR command the input which activates the fast forward,for example, the microcontroller 54 forwards the corresponding controlsignals to the drive of the DVD playback device. Furthermore, themicrocontroller 54 reads from the ROM memory 55 the associatedsubpicture unit for the display of the symbol for the fast forward mode.The microcontroller 54 then notifies the subpicture decoding unit 45,via the control bus, that the display of the last valid subpicture mustbe stopped. The microcontroller 54 then loads the new subpicture unitfor the symbol to be displayed via a separate databus into the internalmemory of the subpicture decoding unit 45. The newly loaded subpictureunit is then simultaneously started via the control bus. The subpicturedecoding unit then inserts the decoded data at the preprogrammedlocations into the bit stream for the entire video picture. For thispurpose, the subpicture decoding unit 45 drives the multiplexing unit 47with correct timing in accordance with the signals for the horizontaland vertical sync pulses, which signals are input into it from the TVsignal coding device 48, and the pixel clock signal. Further detailsregarding the structure and the method of operation of the subpicturedecoding unit 45 are contained in EP-A-0 725 541. In this regard,therefore, reference is expressly made to this document.

It should also be mentioned that for the case of operational menus orstatus displays with dynamic contents, only the rough framework of thesubpicture is stored in the ROM 55 in each case and it is necessary forthe respective subpicture unit to be additionally supplemented in themicrocontroller 54. For this purpose, there must be sufficientread/write memory space in the mircocontroller 54. In the event ofdisplaying the time of day, therefore, the pixel data for therespectively valid numbers must additionally be inserted in each case.This purpose may be served by the use of the invention according to theapplicant's German Patent Application DE 196 53 071.7. The latterdiscloses, namely, how the run length coding of a subpicture must becarried out in order that variable parts in the subpicture (such as, forexample, letters and numbers) can easily be exchanged without decodingof the pixel data having to be carried out.

FIG. 8 now illustrates the flow diagram for the control of thesubpicture decoding unit 45 on the part of the microcontroller 54. Thereference numeral 70 designates the program start. The reference numeral71 designates a program step in which the current subpicture unit in thesubpicture decoding device is stopped. The reference numeral 72designates a program step in which the new subpicture unit for theinsertion of the status information or of the operating menu is loadedinto the subpicture decoding device 45. The reference numeral 73designates a program step in which a register location which waspreviously set in program step 71 is cleared again. The referencenumeral 74 designates a program step in which the newly loadedsubpicture unit in the subpicture decoding device 45 is started. Theprogram ends in program step 75.

The exemplary embodiment of the second solution according to theinvention will now be explained in more detail with reference to FIG. 9.In this case, the corresponding reference numerals in FIG. 9 in eachcase designate the same components as in FIG. 7. A second subpicturedecoding device 61 is additionally provided. The second subpicturedecoding device 61 is likewise connected to the multiplexing unit 47. Inaddition, a control line leads from the second subpicture decodingdevice 61 to the multiplexing unit 47. The multiplexing unit 47 is thuscontrolled by both subpicture decoding units 45 and 61. If a command forthe insertion of a status information item or of an operating menu isnow input into the microcontroller 54, then the microcontroller 54 readsthe corresponding subpicture unit from the ROM 55 and loads thesubpicture unit, possibly after completion, into the second subpicturedecoding device 61. The subpicture unit is also started at the sametime. The two subpicture decoding devices can each process theirsubpicture units separately and output the associated pixel data withcorrect timing to the multiplexing unit 47.

An alternative subpicture decoding device for the exemplary embodimentaccording to FIG. 7 is illustrated in FIG. 10, where the subpicturedecoding device illustrated is designed in such a way that it canprocess two different subpicture units in parallel. For this purpose, ithas provided sufficient memory space for two subpicture units SPU1 andSPU2 in the RAM 60. In addition, two buffer stores 62 and 63 areprovided to which decoded data can be written. The actual decoding unit64 firstly decodes the data of the subpicture unit SUP1. In the process,it writes the decoded data to the first buffer store 62. Subsequently,this decodes the second subpicture unit SPU2 and writes the associateddata to the second buffer store 63. Depending on the status of thehorizontal and vertical sync signals and also of the pixel clock signal,the decoded data are then read either from the first or second bufferstore. In this case, the decoding unit 64 must operate at a speed highenough that the decoded data are already made available when theoutputting of the data with reference to the pixel clock signal isdemanded. However, this can always be achieved if picture-exactoutputting of the subpicture units does not have to be observed, ratherdelayed outputting is sufficient, at least for the status informationand on-screen operational menus.

The invention is not restricted to the exemplary embodiments described.Diverse alterations and modifications are possible. A simple subpicturedecoding device can be designed such that it can generate only fourcolours. In this regard, reference is made to a subpicture decodingdevice which does not contain the special commands for the karaokefunction, namely CHG_COLCON, as specified in the DVD standard. Althoughsuch a subpicture decoding device can generate only four colours for thesubpicture per frame, that has the advantage that the hardware outlayfor the subpicture decoding device is kept low.

It is also possible to provide an expanded subpicture decoding device,which is expanded in such a way that it can process subpicture unitshaving a maximum size of 64 Kbytes instead of 53,220 bytes in accordancewith the DVD standard. In that case, such a subpicture decoding devicecan also generate more complicated subpicture units than is possiblewith the subpicture decoding devices in accordance with the DVD StandardVersion 1.0. The requisite additional hardware outlay remains low.

In a further implementation, it is also possible to design a subpicturedecoding device in such a way that it uses relative pointers having alength of 32 bits instead of the relative pointers having a length of 16bits in accordance with the DVD Standard. Such a subpicture decodingdevice would be able to process subpicture units up to a size of4,294,967,296 bytes. In this case, a higher resolution for thesubpictures would then also easily be possible.

What is claimed is:
 1. Apparatus for generating a digital video picturehaving a main picture with a subpicture and a secondary picturecontaining apparatus status information, comprising: a demultiplexingdevice for separating a bit stream into a main-picture bit stream and asubpicture bit stream; a first decoding unit for decoding themain-picture bit stream; a second decoding unit for decoding thesubpicture bit stream; and, a multiplexing device for outputting decodeddata from the first and second decoding units for concurrent display inthe video picture, where, in response to a command the second decodingunit halts ceases decoding the subpicture bit stream and initiatesdecoding apparatus status information data as the secondary picture. 2.Apparatus according to claim 1, comprising a storage device containingapparatus status information data coded in accordance with thesubpicture data.
 3. Apparatus according to claim 1, wherein thesecondary picture data, coded in accordance with the subpicture data isstored within the second decoding unit.
 4. Apparatus according to claim1, comprising a storage device containing the of apparatus statusinformation and an on screen display menu data coded in accordance withthe subpicture data.
 5. An Apparatus for generating a digital videopicture, having a main picture with a subpicture and a secondarypicture, the secondary picture representing one of apparatus statusinformation and on screen display menu, comprising: a demultiplexingdevice for separating an input bit stream into a main-picture bit streamand a subpicture bit stream; a first decoding unit for decoding themain-picture bit stream consisting of compressed data representing themain picture; a second decoding unit for decoding compressed data of thesubpicture bit stream; a third decoding unit for decoding compresseddata representative of the secondary picture; and, a multiplexing devicefor outputting in a timed sequence, data decoded from the first, secondand third decoders for concurrent presentation in the video picture;wherein the compressed data representing the subpicture and thesecondary picture are coded with substantially similar rules and withthe same format as the subpicture bit stream, the second and thirddecoding units are correspondingly substantially similarly.
 6. Theapparatus of claim 5, comprising a storage device, containing compresseddata representative of the secondary picture.
 7. The apparatus of claim6, wherein the second decoding and third decoding units are combined toform a common decoding unit for successively decoding the subpicture andsecondary picture data for timed insertion in the main picture data bythe multiplexing device.
 8. Apparatus for generating a digital videopicture having a main picture with a subpicture and a secondary picturecontaining one of apparatus status information and an on screen displaymenu, comprising: a demultiplexing device for separating a bit streaminto a main-picture bit stream and a subpicture bit stream; a firstdecoding unit for decoding the main-picture bit stream; a seconddecoding unit for decoding the subpicture bit stream; and, amultiplexing device for outputting decoded data from the first andsecond decoding units for concurrent display in the video picture,where, in response to a command the second decoding unit halts decodingthe subpicture bit stream and initiates decoding one of apparatus statusinformation and on screen display menu data as the secondary picture.